[Buildroot] [Bug 10796] New: Cannot generate cpio image without selecting CONFIG_BLK_DEV_INITRD

[Buildroot] [Bug 10796] New: Cannot generate cpio image without selecting CONFIG_BLK_DEV_INITRD

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=10796

            Bug ID: 10796
           Summary: Cannot generate cpio image without selecting
                    CONFIG_BLK_DEV_INITRD
           Product: buildroot
           Version: 2017.08
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: Other
          Assignee: unassigned at buildroot.uclibc.org
          Reporter: adyke at harris.com
                CC: buildroot at uclibc.org
  Target Milestone: ---

If BR2_TARGET_ROOTFS_CPIO is selected, the next time linux-menuconfig is run
CONFIG_BLK_DEV_INITRD becomes selected. If CONFIG_BLK_DEV_INITRD is unselected,
it is silently reselected when linux-menuconfig exits.

Therefore, it is not possible to generate rootfs.cpio without building it into
the kernel image.

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[Buildroot] [Bug 10796] Cannot generate cpio image without selecting CONFIG_BLK_DEV_INITRD

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=10796

--- Comment #1 from Thomas Petazzoni <thomas.petazzoni@free-electrons.com> ---
Indeed, linux/linux.mk contains:

        $(if $(BR2_TARGET_ROOTFS_CPIO),
                $(call KCONFIG_ENABLE_OPT,CONFIG_BLK_DEV_INITRD,$(@D)/.config))

Which forces CONFIG_BLK_DEV_INITRD to be set when you're generating a cpio
image of the filesystem.

What is your use-case for generating a cpio image, but not enabling
CONFIG_BLK_DEV_INITRD ?

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[Buildroot] [Bug 10796] Cannot generate cpio image without selecting CONFIG_BLK_DEV_INITRD

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=10796

--- Comment #2 from adyke at harris.com ---
(In reply to Thomas Petazzoni from comment #1)
My use case is to generate a build that can be made into a disk image and also
be PXE booted. For PXE booting, I need the cpio file. But for installing to
disk, I don't want the root filesystem built in to the kernel.

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[Buildroot] [Bug 10796] Cannot generate cpio image without selecting CONFIG_BLK_DEV_INITRD

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=10796

Arnout Vandecappelle <arnout@mind.be> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |WONTFIX
             Status|NEW                         |RESOLVED

--- Comment #3 from Arnout Vandecappelle <arnout@mind.be> ---
(In reply to adyke from comment #2)
CONFIG_BLK_DEV_INITRD does not link the cpio image into the kernel. It only
makes it possible that the bootloader passes a cpio image to the kernel. To
link it into the kernel, the option CONFIG_INITRAMFS_SOURCE must be non-empty.

Buildroot will set this option when you enable the "initial RAM filesystem
linked into linux kernel". However, when you unset this option again, the
CONFIG_INITRAMFS_SOURCE is *not* removed from the kernel configuration. Indeed,
Buildroot has no way to know if this was added by Buildroot itself, or if it
was set by the user to refer to an externally-generated initramfs. So I guess
you are in this situation.

The CONFIG_BLK_DEV_INITRD option is on in most defconfig and just has a few KB
overhead, so it is not worth removing this from linux.mk IMO. Therefore, I'm
marking this as WONTFIX.

If you disagree, or if you see some other problem, feel free to reopen.

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